Apparatus for and methods of stress testing metal components

ABSTRACT

A tuning device ( 23 ) and an apparatus that incorporates the tuning device ( 23 ) for use in testing the integrity of a railway line ( 30 ) to obtain an improved test signal, the tuning device ( 23 ) including an elongate member ( 23 ) adapted to be attachable at one end of the railway line ( 30 ) being tested in situ or is attachable to an attachment member ( 21 ) coupled to the section ( 10 ) of railway line ( 30 ), and wherein a vibration signal measuring means ( 24 ) is adapted to be secured to the other end of the elongate member ( 23 ). The apparatus can include a control means ( 2 ), a vibration means ( 3 ), the tuning device ( 23 ) configured and arranged to be attachable to the railway line ( 30 ) and a vibration measuring means ( 24 ) is attachable to the railway line ( 3 ) to directly vibrate the section ( 10 ) of the railway line ( 30 ), the control means ( 2 ) controlling the frequency of vibration and to receive and process measurements of the amplitude of vibration from the tuning device ( 23 ) and the frequency of vibration from the vibration measuring means ( 24 ).

TECHNICAL FIELD

This invention relates to improvements in and relating to devices andapparatus for testing metal components, and methods and systemsassociated therewith. More particularly, but not exclusively, thisinvention relates to methods of testing the integrity of railway lines.

BACKGROUND ART

Metal components suffer from a degree of residual stress caused byactions such as mechanical or thermal loading. The presence of stressaffects the physical properties of a metal component and can result instress fatigue and even failure of a component.

Methods available for measuring residual stress in metal components arenot in widespread usage. Current practice is generally simply to subjecta metal component to thermal stress relieving techniques regardless ofthe actual need. Therefore a significant wastage of resources arises inheat treating metal components not requiring stress relief.

A related problem arises with elongate components such as railway linesand pipelines. A railway track is generally laid in such a way as to beunder a neutral load condition at a predetermined temperature. When thetrack is above the neutral temperature the railway line as a whole isplaced under compression as the sections expand. At excessive levelsthis can result in the track buckling. At temperatures lower than theneutral temperature the track lengths exist in tension. At some point ifthe tensile forces are high enough, ie the temperature is low enough,the sections of track can snap.

Because of the outcome of the snapping of sections of track is not asmuch of a safety hazard as buckling of track the neutral temperature istypically set above the average summertime temperature. In New Zealandthe neutral temperature is set at around 30 degrees Celsius.

Railway lines undergo considerable thermal cycling. They are alsosubjected to significant mechanical loading as trains ride over therails. This can result in plastic deformation of the rails, that is, therails stretch. When that happens the neutral temperature of the railsdrops, and thus the risk of track buckling on hot days increases. It isgenerally accepted that railway lines need to be reset or restretched.More particularly, they need to be re-laid under tension in order toreset the neutral temperature every ten years or so to minimise the riskof buckling. At present it is a costly and time consuming exercise touplift a railway line to restretch and relay it. Significant resourcescan be wasted on restretching sections of track that do not require anystretching.

It is an object of the invention to provide a device and/or an apparatusfor use in testing the integrity of metal components and sections ofrailway line that overcomes at least some of the abovementionedproblems, or at least to provide the public with a useful choice.

SUMMARY OF THE INVENTION

According to a broad aspect of the invention there is provided a tuningdevice for use in testing the integrity of a railway line to obtain animproved test signal, the tuning device including an elongate memberadapted to be attachable at one end to the railway line being tested insitu or is attachable to an attachment member coupled to the section ofrailway line, and wherein a vibration signal measuring means is adaptedto be secured to the other end of the elongate member.

Preferably the vibration signal measuring means is a transducer means.Desirably the transducer means is an accelerometer.

Preferably the elongate member is made of a suitable metal. Desirablythe tuning device is made of a non-brittle, high tensile, material thathas a sufficient amount of elasticity and ductility.

Advantageously the elongate member is fastened to an attachment member,and wherein the attachment member is releasably clamped to the head of arailway line. Desirably the attachment member is an L shaped block ofmetal that is mild steel.

Preferably a dampening means is secured to the elongate member adjacentthe vibration signal measuring means to allow for the tuning frequencyof the tuning device to be set. Desirably the dampening means is tubularand is provided with a hollow central section, and wherein a dampeningmaterial is provided within the hollowed central section.

Preferably in one application of the testing apparatus the elongatemember is substantially about 13.5 centimeters between an attachmentpoint on the railway line or attachment member and the vibration signalmeasuring means, and the elongate member is substantially about 16millimeters in width and about 3 millimetees in thickness, and whereinthe tuning device is tuned to measure frequencies at about 80 Hertz.

According to a second aspect of the invention there is provided anapparatus for testing the integrity of a section of railway lineincluding a control means, a vibration means, a tuning device configuredand arranged to be attachable to said section of railway line inaccordance with the first aspect of the invention, and a vibrationmeasuring means, the vibration means being associated with a saidsection of railway line, in use, to directly vibrate the section ofrailway line, the control means controlling the frequency of vibrationand to receive and process measurements of the amplitude of vibrationfrom the tuning device and the frequency of vibration from the vibrationmeasuring means.

Preferably the apparatus further includes a temperature measurementmeans attachable to the said section of railway line to provide atemperature signal to the control means.

Desirably the vibration means is a motor having eccentric weightsmounted about the motor shaft, and wherein the vibration measurementmeans is a tachometer mounted to the shaft of the motor.

Advantageously the distance between the tuning device and the vibrationmeans is any suitable distance to achieve accurate test measurements andis desirably between substantially about 60 to 70 centimeters but itwill be appreciated that variants of these measurements are possiblewithin the scope of the invention.

According to a third aspect of the invention there is provided a systemof testing the integrity of a section of railway line, the systemincluding the apparatus of the second aspect of the invention associatedwith a section of railway line running over five consecutive railwaysleepers aligned transversely under the railway line, the vibrationmeans, in use, being coupled to the railway line adjacent the secondsleeper and an accelerometer or the tuning device according to any oneof claims 1 to 10 being attachable to the section of railway lineadjacent the fourth sleeper, and wherein the distance between thevibration means and the accelerometer or the tuning device is betweenabout 60 to 75 centimeters.

Preferably the system is configured and arranged wherein the second,third and fourth sleepers are unclipped from the railway line andpacking members are placed between the top of the second and fourthsleepers and the underside of the railway line respectively to form anair gap between the third sleeper and the underside of the railway line.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be illustrated, by wayof example only, with reference to the accompanying drawings in which:

FIG. 1: illustrates a block diagram of general components of theapparatus of the invention;

FIG. 2: illustrates the system of attachment of the apparatus of FIG. 1to a section of railway line;

FIG. 3: illustrates the tuning device and an arrangement on anattachment member; and

FIG. 4: illustrates one form of attachment of the tuning device to asection of railway line.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1, a block diagram of general components of theapparatus of the invention, generally referred to as 1, is illustrated.

The apparatus 1 can be provided to test the integrity of a metalcomponent. The metal component can desirably be of any suitable type fortesting purposes by vibration. It will be appreciated that referencesherein to a railway line can also be references to other metalcomponents, including pipelines. However, for simplicity of descriptionof the invention the embodiments thereof will refer herein to railwaylines.

Further, this invention is related to the invention as described in WO97/04291 and U.S. patent specification No. 6,026,687 and the fulldescription of the patentee's invention as described in those documentsis incorporated herein as part of this description. A person skilled inthe art would have ready access to those documents and the descriptioncontained therein when seeking to appreciate and understand aspects ofthe present invention.

The apparatus 1 preferably includes a control means 2 in the form of acomputer means having a microprocessor programmed to control theoperation of the apparatus 1 and including the steps of obtainingmeasurements and data from the various measuring instruments, processingthe inputted signals into a desirable form suitable for storage and/ordisplay purposes. With respect to storage purposes the data may bemanipulated to provide statistical data showing characteristics of therailway line or section of railway line 10 being tested.

The control means 2 can function to control each step of the method ofthe invention. The control means 2 can desirably be powered by anysuitable and durable battery means (not shown) for remote testing on sayrailway track away from an electrical power source and to allow theapparatus to have portable applications rather than merely laboratoryworkbench applications.

A vibration means 3 can be mounted by any known and suitable securingmeans, such as for example a clamp, to an appropriate area of therailway line. Desirably the vibration means is in the form of a motoradapted with a vibration inducement means preferably in the form ofeccentric weights mounted to the motor shaft that apply a vibrationforce on the line. Such force is adjustable such that the frequency ofvibration can be changed as required. The vibration means 3 may includean exciter or shaker, as it is known in the art, that is desirablycontrolled by a user controlling and adjusting the speed of the motor 3.The motor 3 can be controlled by being associated with the control means2.

The motor speed of the vibration means can be sensed using any knownform of motor speed measuring means and in this embodiment is in theform of a tachometer 4 that can be mounted to the shaft of the motor 3.The tachometer 4 measures the shaft speed and the measured signaloutputs are fed to the control means 2.

The amplitude of vibration induced on a section of railway line issensed and measured using a signal measuring means in the form of atransducer means, desirably an accelerometer 5. It will be appreciatedthat any suitable known instrument may be used or applied.

The accelerometer 5 generates an electrical signal in response to thevibration acceleration of the railway line as induced by the vibrationmeans 3, and provides a signal that is fed to the control means 2. Thecontrol means 2 is configured and arranged to convert the signals into ameasurement of frequency of vibration.

A temperature measurement means 6 with a suitably sensitive sensingmeans can measure the temperature of the line during measurements. Thetemperature measurements means 6 is desirably in the form of a pyrometerand provides a measurement to the control means 2 that allows thetemperature of the line to be tagged against other recorded data at thetime of testing.

A display means 7 can be provided to display the plotted measurements ofvelocity amplitude (for example, in mm/second) against the frequency ofvibration and any other desirable characteristics of the data obtainedin the testing phase of the operation.

Referring now to FIG. 2, a system of attachment of the apparatus 1 to asection of railway line before testing of the said section of railwayline, is illustrated.

Persons skilled in the art will appreciate that railway lines undergoconstant compression or tension caused by changes to temperature aboutthe line and other factors. Rapid changes in temperature or unacceptablyhigh or low temperatures can induce undesirable levels of stress thatcan cause railway lines to buckle.

Some railway lines are joined in sections. Adjoining sections of linemust be laid at a similar level of tension or compression, and can bedesirably laid at a neutral state at a certain temperature. If adjoiningsections are in a substantially different state and temperaturefluctuations are rapid, buckling or other undesirable movements in theline can occur. The invention can assist with testing the integrity ofrailway lines to determine whether relaying or replacement of sectionsof line is required, and may provide an aid to the proper laying orrelaying of railway lines.

In one non-limiting method and system of testing, a section of railwayline 10 for testing is seen in FIG. 2 as resting on five railwaysleepers, defined as first sleeper A, second sleeper B, third sleeper C,fourth sleeper D, and fifth sleeper E. These five sleepers can beunclipped from the line to be tested or may be left clipped in positionduring testing, as required. The first sleeper A and the fifth sleeper Ecan be preferably rigidly secured and having ballast compacted and incontact with the sides of the first sleeper A and the fifth sleeper Esuch that the underside of the sleepers A and E can be in contact withthe ballast. It will be appreciated by one skilled in the art thatballast can also be used on other sleepers as required to ensure propercontact during testing.

The second sleeper B, the third sleeper C and the fourth sleeper D canbe unclipped from the line 10. A packing member 11 in the form of a shimor the like is placed between the top of the second sleeper B and theunderside of the line 10. A shim 11 can also be placed between the topof the fourth sleeper D and the underside of the railway line 10. A gapis advantageously left between the top of the third sleeper C and theunderside of the railway line 10, generally indicated by 12.

The arrangement of the second, third and fourth sleepers relative to theline 10 can be considered important for one form of testing inaccordance with the system of testing using the apparatus 1.

The accelerometer 5 can be mounted to the line 10 desirably above thefourth sleeper D. Advantageously the accelerometer 5 is mounted in atuning arrangement as described below with reference to FIGS. 3 and 4.The vibration means 3 can be coupled or mounted above the second sleeperB. The temperature measurement means 6 can be mounted in any suitableposition on the line 10. All necessary data lines are connected to thecontrol means 2 by hard wire 13 or otherwise, such as, for example,infra red or laser signal. Any known methods of data communications maybe employed as required.

In one operation, a method of testing the integrity of the line 10 isdescribed. The vibration means 3 is activated and the accelerometer 5provides a feedback signal to the control means 2. The signal can beprocessed to a digital form and a display means 7 displays a plot of thevelocity amplitude of vibration (mm/sec) against the frequency ofvibration (hertz). The frequency of vibration can be increased,generally in most applications testing can be achieved in the operatingfrequency range of between 0 to 100 hz in some situations but may beincreased to any suitable frequency up to substantially 500 Hz orthereabouts as required. A reasonably linear measurement of amplitude ofvibration is measurable by the accelerometer 5 that can also bedisplayed. The vibration may be increased until a noticeable spike isdetected.

With some railway lines a spike or loading node may be detected atbetween 50 hz and 125 hz. If the line is in tension the spike may bedetected between 50 hz and 75 hz. If the line is in compression anoticeable spike is detectable at between about 85 hz and 100 hz. Thisinformation is useful for determining whether a section of railway linerequires re-stretching or replacement and provide an indication of thecondition of the line 10.

It will be appreciated that in one alternative embodiment, theaccelerometer 5 may be placed between the sleeper C and sleeper D andthe vibration means 3 mounted above the second sleeper B to allowdesirable and accurate measurements to be obtained in accordance withthe invention. The accelerometer 5 and the vibration means 3 shouldpreferably be mounted at least 60 cm apart.

Referring now to FIGS. 3 and 4, a tuning arrangement for obtaining anelectrical signal representing the frequency of vibration on a railwayline, generally referred to as 20, is illustrated.

The tuning arrangement 20 is designed to improve the quality of thesignal by reducing errors caused by the standard clamping systemincorporated with attaching or coupling an accelerometer directly to therailway line.

A tuning device may desirably include an attachment member in the formof a base member 21 that functions to anchor or couple the signalmeasuring means or transducer means to the railway line 30. The basemember 21 may be preferably in the form of an L-cross section and islarge enough to allow any suitable and durable clamping means 22 toclamp the tuning arrangement to the line 30. As seen clearly in FIG. 4,desirably the base member 21 is clamped to the outside of the line 30 asit is considered to be an area of the line that does not wear to thesame extent as the inside head section of a standard two rail line.

A tuning device 23 is made of any suitable and durable material, andfunctions to couple the transducer means in the form of an accelerometer24 base member 21 via the elongate member 23 and allow accuratemeasurements to be taken. A non-brittle elastic material can be suitablyused, and a high tensile mild steel metal is desirable, as it is toughand ductile. A light metal with a high elasticity can be advantageous.

The near end of the elongate member 23 can be located in a slot (notshown) in an edge of the base member 21 for increased coupling andattached to the base member 21 by any suitable attachment means. In thisexample screws 25 are shown. The accelerometer 24 can be secured to theelongate member 23 at the distal end. A dampening means 26 may beincluded adjacent the accelerometer 24 at the distal end of the elongatemember 23.

The dampening means 26 may desirably be in the form of a tubulardampener 26 having a hollow section allowing a material to be addedwithin to set the desired tuning frequency of the tuning arrangement.Desirably sand is used in the dampener. In one desirable embodiment thedampener 26 can possibly be about 15 millimeters (“mm”) in height andabout 3 millimeters in diameter. Other dimensions and shapes areenvisaged within the scope of the invention.

In one non-limiting example, the elongate member 23 can be about 13.5 cmbetween the screw 25 and the accelerometer 24 and be about 16 mm inwidth and about 3 mm in thickness. These dimensions may be provided whenthe tuning device is being used to measure frequencies at about 78 hz or80 hz.

It may well be that a more sensitive tuning device 23 can be providedwhen the thickness of the device 23 is reduced.

It will be appreciated that when the base member 21 is clamped to theline the tuning device 23 is in parallel with the railway line. It isconsidered to be desirable to have the tuning device 23 in parallel withthe railway line for increased accuracy.

In yet a further embodiment or set up arrangement for testing as analternative to the previous methods as described with reference to FIG.2, no shims or packing need be used, and the railway line 30 can remainclipped to the sleepers.

In this method with unclipped railway lines, the vibration means 3 islocated over sleeper B, and the base member 21 is clamped, and morepreferably can be T-clamped, to the line between sleeper C and sleeperD, and desirably halfway between sleeper C and sleeper D. The coupledtuning device 23 and accelerometer 24 may be positioned at about atleast 60 cm from the vibration means 3 and more preferably substantiallyabout 70 cm from the tuning device 23 to obtain more accurate resultsand to avoid or minimlise interference from the vibration means 3.

Advantageously, the feedback signal from the accelerometer 5 to thecontrol means 2 can be provided to the control means 2 via an infra redor laser signal means. The receiver for the infra red or laser signalmay be attached to a rail car that is movable on the line, and whereinthe testing and measuring apparatus of the invention is located.

It is considered that one desirable tuned frequency is 80 hz as it isconsidered a suitable frequency for testing resulting in reasonableamplification of the velocity amplitude signals sensed by theaccelerometer 24. This is bearing in mind that the resonant frequenciesof many railway lines are well above this frequency.

The invention further includes suitable computer software forcontrolling the operation of the computer or computer means that formspart of the control unit 2. Preferably the computer processing steps forcontrolling the operation of the apparatus for testing the integrity ofa railway line includes the steps of obtaining data on the frequency ofvibration of the line by using a suitable measuring device such as atachometer. It will be appreciated that close control of the vibrationmeans is possible using the tachometer to sense motor speed and toprovide a signal to the control unit 2. The control unit 2 may thenprovide a signal to adjust motor speed as appropriate.

The accelerometer 5 provides a signal of the amplitude of vibration ofthe line. The temperature measurement means 6 desirably provides asignal of the temperature of the line.

Once this data has been obtained, the next step is executed in that agraph can be plotted showing the amplitude of vibration against thefrequency of vibration at a determined temperature of the line. Theresultant data is then recorded and can be later compared against otherderived data as required.

Preferably the computer processing steps further include the step ofcomparing the plots for a section of line being tested at different linetemperatures and determining whether the line is in compression ortension.

Desirably the processing steps included the preliminary step ofobtaining a reference measurement of the velocity amplitude of the linewhen in a neutral position defined as being neither in compression ortension. This measurement can be recorded for comparison purposes forall plots at different line temperatures.

Wherein the aforegoing reference has been made to integers or componentshaving known equivalents, then such equivalents are herein incorporatedas if individually set forth. Accordingly, it will be appreciated thatchanges may be made to the above described embodiments of the inventionwithout departing from the principles taught herein.

Additional advantages of the present invention will become apparent forthose skilled in the art after considering the principles in particularform as discussed and illustrated. Thus, it will be understood that theinvention is not limited to the particular embodiments described orillustrated, but is intended to cover all alterations or modificationswhich are within the scope of the appended claims.

1. A tuning device for use in testing the integrity of a railway line toobtain a vibration test signal, the tuning device including an elongatemember adapted to be attachable at one end to the railway line beingtested in situ or is attachable to an attachment member coupled to thesection of a said railway line so as to allow, in use, the other end ofthe elongate member to extend freely therefrom, the elongate memberbeing made of a non-brittle and elastic material suitable for enabling avibration signal measuring means to be securable to the elongate member,in use, so as to measure the vibration signals on the said railway line.2. A tuning device in accordance with claim 1 wherein the vibrationsignal measuring means is a transducer means.
 3. A tuning device inaccordance with claim 2 wherein the transducer means is anaccelerometer.
 4. A tuning device in accordance with claim 1 wherein theelongate member is made of mild steel.
 5. A tuning device in accordancewith claim 1 wherein the elongated member is made of a non-brittle, hightensile, material that has sufficient elasticity and ductility.
 6. Atuning device according to claim 1 wherein the one end of the elongatemember is fastenable to an attachment member, and wherein the attachmentmember is a block of metal, in use, that is releasably clampable to thehead of a railway line.
 7. A tuning device according to claim 1 whereinthe attachment member is an L shaped block of metal adapted to bereleasably clampable to the head of a railway line.
 8. A tuning deviceaccording to claim 1 wherein a dampening means is secured to theelongate member adjacent the vibration signal measuring means to allowfor the tuning frequency of the tuning device to be set.
 9. A tuningdevice according to claim 1 wherein the dampening means is tubular andis provided with a hollow central section, and wherein a dampeningmaterial is provided within the hollowed central section.
 10. A tuningdevice according to claim 1 wherein the elongate member is substantiallyabout 13.5 centimeters between an attachment point on the railway lineor attachment member and the vibration signal measuring means, and theelongate member is substantially about 16 millimeters in width and about3 millimeters in thickness, and wherein the tuning device is tuned tomeasure frequencies at about 80 Hertz.
 11. An apparatus for testing theintegrity of a section of railway line, the apparatus including acontrol means, a vibration means, a tuning device including an elongatemember adapted to be attachable at one end to the railway line beingtested in situ or is attachable to an attachment member that is in turncoupled to the section of a said railway line so as to allow, in use,the other end to extend freely therefrom, the elongate member being madeof a non-brittle and elastic material suitable for enabling a vibrationsignal measuring means to be secured to the elongate member, in use, soas to measure vibration signals on the said railway line and thevibration signal measuring means, the vibration means being associatedwith a said section of railway line, in use, to directly vibrate thesection of railway line, the control means controlling the frequency ofvibration and to receive and process measurements of the amplitude ofvibration from the vibration signal measuring means of the tuning deviceand the frequency of vibration from the vibration means.
 12. Anapparatus according to claim 11 further including a temperaturemeasurement means attachable to the said section of railway line toprovide a temperature signal to the control means.
 13. An apparatusaccording to claim 11 wherein the vibration means is a motor havingeccentric weights mounted about the motor shaft, and wherein thevibration measurement means is a tachometer mounted to the shaft of themotor.
 14. An apparatus according to either claim 11 or claim 12 whereinthe distance between the tuning device and the vibration means isbetween about 60 to 70 centimeters.
 15. A system of testing theintegrity of a section of railway line, the system including anapparatus having a control means, a vibration means, and a tuningdevice, the tuning device comprising an elongate member adapted to beattachable at one end to the railway line being tested in situ or isattachable to an attachment member that is in turn coupled to thesection of a said railway line so as to allow, in use, the other end toextend freely therefrom and being substantially in parallel to the saidrailway line, the elongate member being made of a non-brittle andelastic material suitable for enabling a vibration signal measuringmeans to be secured to the elongate member, in use, so as to measurevibration signals on the said railway line, and the vibration signalmeasuring means, the vibration means being associated with a saidsection of railway line, in use, to directly vibrate the section ofrailway line, the control means controlling the frequency of vibrationand to receive and process measurements of the amplitude of vibrationfrom the vibration signal measuring means of the tuning device and thefrequency of vibration from the vibration means, the apparatus being setup on a section of railway line running over five consecutive railwaysleepers aligned transversely under the railway line, the vibrationmeans, in use, being coupled to the railway line adjacent the secondsleeper and an accelerometer or the tuning device being attachable tothe section of railway line adjacent the fourth sleeper, and wherein thedistance between the vibration means and the accelerometer or the tuningdevice is between about 60 to 75 centimeters.
 16. A system according toclaim 15 wherein the second, third and fourth sleepers are unclippedfrom the railway line and packing members are placed between the top ofthe second and fourth sleepers and the underside of the railway linerespectively to form an air gap between the third sleeper and theunderside of the railway line.